base16ct/
lower.rs

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1use crate::{decode_inner, encoded_len, Error};
2#[cfg(feature = "alloc")]
3use crate::{decoded_len, String, Vec};
4
5/// Decode a lower Base16 (hex) string into the provided destination buffer.
6pub fn decode(src: impl AsRef<[u8]>, dst: &mut [u8]) -> Result<&[u8], Error> {
7    decode_inner(src.as_ref(), dst, decode_nibble)
8}
9
10/// Decode a lower Base16 (hex) string into a byte vector.
11#[cfg(feature = "alloc")]
12pub fn decode_vec(input: impl AsRef<[u8]>) -> Result<Vec<u8>, Error> {
13    let mut output = vec![0u8; decoded_len(input.as_ref())?];
14    decode(input, &mut output)?;
15    Ok(output)
16}
17
18/// Encode the input byte slice as lower Base16.
19///
20/// Writes the result into the provided destination slice, returning an
21/// ASCII-encoded lower Base16 (hex) string value.
22pub fn encode<'a>(src: &[u8], dst: &'a mut [u8]) -> Result<&'a [u8], Error> {
23    let dst = dst
24        .get_mut(..encoded_len(src))
25        .ok_or(Error::InvalidLength)?;
26    for (src, dst) in src.iter().zip(dst.chunks_exact_mut(2)) {
27        dst[0] = encode_nibble(src >> 4);
28        dst[1] = encode_nibble(src & 0x0f);
29    }
30    Ok(dst)
31}
32
33/// Encode input byte slice into a [`&str`] containing lower Base16 (hex).
34pub fn encode_str<'a>(src: &[u8], dst: &'a mut [u8]) -> Result<&'a str, Error> {
35    encode(src, dst).map(|r| unsafe { core::str::from_utf8_unchecked(r) })
36}
37
38/// Encode input byte slice into a [`String`] containing lower Base16 (hex).
39///
40/// # Panics
41/// If `input` length is greater than `usize::MAX/2`.
42#[cfg(feature = "alloc")]
43pub fn encode_string(input: &[u8]) -> String {
44    let elen = encoded_len(input);
45    let mut dst = vec![0u8; elen];
46    let res = encode(input, &mut dst).expect("dst length is correct");
47
48    debug_assert_eq!(elen, res.len());
49    unsafe { String::from_utf8_unchecked(dst) }
50}
51
52/// Decode a single nibble of lower hex
53#[inline(always)]
54fn decode_nibble(src: u8) -> u16 {
55    // 0-9  0x30-0x39
56    // A-F  0x41-0x46 or a-f  0x61-0x66
57    let byte = src as i16;
58    let mut ret: i16 = -1;
59
60    // 0-9  0x30-0x39
61    // if (byte > 0x2f && byte < 0x3a) ret += byte - 0x30 + 1; // -47
62    ret += (((0x2fi16 - byte) & (byte - 0x3a)) >> 8) & (byte - 47);
63    // a-f  0x61-0x66
64    // if (byte > 0x60 && byte < 0x67) ret += byte - 0x61 + 10 + 1; // -86
65    ret += (((0x60i16 - byte) & (byte - 0x67)) >> 8) & (byte - 86);
66
67    ret as u16
68}
69
70/// Encode a single nibble of hex
71#[inline(always)]
72fn encode_nibble(src: u8) -> u8 {
73    let mut ret = src as i16 + 0x30;
74    // 0-9  0x30-0x39
75    // a-f  0x61-0x66
76    ret += ((0x39i16 - ret) >> 8) & (0x61i16 - 0x3a);
77    ret as u8
78}
base16ct/lower.rs

base16ct/
lower.rs
